POS0310 DO AXIAL PSORIATIC ARTHRITIS PATIENTS MEET ASAS CLASSIFICATION CRITERIA FOR AXIAL SPONDYLOARTHRITIS?
Authors: E. Gubar, T. Korotaeva, E. Loginova, Y. Korsakova, S. Glukhova
Journal: Annals of the Rheumatic Diseases (2022)

Background There isn’t any generally accepted definition and diagnostic criteria for axial psoriatic arthritis (axPsA). According to most recent data, classification criteria for axial spondyloarthritis (axSpA) may not be applied to axPsA (1). Objectives To analyze, in clinical practice, whether axPsA patients (pts) meet classification criteria for axSpA and ankylosing spondylitis (AS). Methods 52 pts (M/F–32/20), a hospital cohort, with PsA according to CASPAR criteria were observed. All pts had back pain at one time or another, which rheumatologist suspected to be axial involvement. Pts’ age 43.0 [35.0; 54.0], disease duration 3.4 yrs [0.2; 32.0]. Ме BASDAI 5.3 [3.6; 7.0]; ASDAS-СРБ 3.3 [2.2; 4.1]; DAPSA 36,3 [19,3; 50,5]; CRP 9.6 [0.1; 86.6] mg/L; ESR 31 [3; 99] mm/h. Enthesitis was found in 69.2% and dactylitis in 61.5% of pts. All pts had psoriasis with Ме BSA (body surface area) of 4 [1; 9]%, Ме PASI (Psoriasis Area Severity Index) of 9.6 [5.6; 17.4]. Nail psoriasis was found in 38 (73.1%) pts, 40.4% of them had onycholysis. All pts were evaluated for presence of inflammatory back pain (IBP) by ASAS criteria. Pts underwent sacroiliac joints (SIJ) X-ray (pelvic radiographs), cervical and lumbar spine, hands and feet X-rays, so that 50 pts had complete sets of radiographs. Radiographic sacroiliitis (rSI) was defined as bilateral grade ≥ 2 or unilateral grade ≥ 3. Pts without rSI underwent SIJ MRI on Philips Multiva 1.5 T scanner. Active MRI sacroiliitis (MRI-SI) was categorized using ASAS 2016 criteria. Radiographic spondylitis (rSp) was defined as ≥1 marginal/paramarginal syndesmophyte(s) of the cervical and/or lumbar spine. All radiographs and MRI results were interpreted by two experienced musculoskeletal radiologists. 45 pts underwent HLA B27 examination. Me [Q25; Q75] and Pierson-χ2 tests were performed. All p&lt;0.05 were considered to indicate statistical significance. Results IBP was found in 34 (66.7%) and rSI in 30 (57.7%) pts. 15 (30.0%) pts had rSI along with rSp, while in 15 (30.0%) pts rSI was without it, and 9 (18.0%) pts had rSp alone. 2 pts of the 17 examined, had MRI-SI. HLA B27 was present in 15 (33.3%) pts examined. 37 (71.2%) pts met ASAS criteria for axSpA as follows: 22 pts met the imaging arm (rSI or MRI-SI + ≥ 1SpA feature), 5 pts met the clinical arm (HLA B27+ ≥ 2 other SpA features) and 10 pts met both of those. 10 (19.2%) pts didn’t meet ASAS criteria for axSpA: they had neither rSI/ MRI-SI nor HLA B27; however, 9 of them had syndesmophytes. 30 pts had rSI with 21 of them (40.4% of all pts) meeting modified New York (mNY) criteria for AS, because along with rSI, they had at least 1 of the 3 clinical criteria (IBP for &gt; 3 months, limitation of lumbar motion in sagittal and frontal planes, limitation of chest expansion). The pts who met both CASPAR and mNY criteria, however had typical axPsA features: 85.7% of them had polyarthritis with multiple joint erosions, 61.9% had osteolysis and/or juxtaarticular new bone formation, 61.9% dactylitis, 33.3% non-marginal asymmetrical syndesmophytes, 44.4% were HLA B27 negative, 43.3% didn’t have IBP; all pts developed psoriasis many years before the onset of PsA. Conclusion Among PsA pts with axial involvement there is an alternative phenotype group (18% of our cohort) with neither sacroiliitis (rSI/ MRI-SI) nor HLA B27. Such pts do not meet ASAS criteria for axSpA. The alternative phenotype is characterized by isolated spondylitis (syndesmophytes) without sacroiliitis. Axial disease cannot be ruled out in PsA pts without spinal radiographs, regardless of symptoms. Pts meeting both CASPAR and mNY criteria and featuring typical axPsA symptoms cannot be diagnosed as having AS along with concomitant psoriasis, because axPsA and AS with psoriasis seem to be two different diseases. There is an urgent need for a unified definition of axial involvement in PsA. References [1]LC Coates et al. Arthritis Care Res.2021;73(6):856-860 Disclosure of Interests ELENA GUBAR: None declared, Tatiana Korotaeva Speakers bureau: Pfizer, MSD, Novartis, AbbVie, Janssen, Lilly, Celgene, JSC BIOCAD and Novartis-Sandoz, Elena Loginova Speakers bureau: Janssen, Yulia Korsakova Speakers bureau: Novartis, Svetlana Glukhova: None declared